Zelda_pinwheel was writing her explanations on what to do
way past her bedtime!!! 
She has given you some great ideas to further explore, like
Mobi2IMP and
lit2sb (i.e. .lit to .imp).
Allow me to further elaborate since these programs can be found here in the Fictionwise fourm, namely
Mobi2IMP 9.4 with new Windows GUI & UTF-8 and
Convert .lit directly into .IMP formats. I would also recommend, in the Format Conversion forum,
PDFRead 1.8.2 released! for all your .pdf/.djvu converting needs.
The above programs are mainly useful in creating .imp ebooks using previously created ebooks (in a different format like .prc/.pdb/.lit/.pdf). I have a lot of hands-on experience with these programs since most were created/exploited by me.
For creating your own .imp ebooks from .html source, the most powerful software to use is
eBook_Publisher. It has a steep learning curve, but what powerful software doesn't.
Ok, now enough with the introductory stuff, let's get you creating .imp ebooks:
- First, eBook Publisher requires that you to create a
New Project (.opf file) using the File menu item.
- Next, you should enter the ebook details using
Edition Setting... under the Project menu and save it using the name of your resulting .imp ebook. Ensure you uncheck "Require ISBN", enter Title, Author and Bookshelf Category at a minimum as these are required entries.
- Next, you can
Add Files... any source .html, just change the file-requester's filetype from *.odf to *.html.
- Next make sure you change the
Build Target from the default "OEBFF: All Targets" to "Grayscale Half-VGA" for the eBookwise 1150 .imp format.
- Last, select
Build Edition... and determine if the
Processing Successful message appears as the last line of the Errors and Messages window. If not, you may need to tweak your source .html and repeat
Build Edition... until you are satisfied with the .imp output.
To get the .imp file onto the reader, just follow
this.
Obviously, this is just a very cursory step-by-step, but it should point you in the direction. And yes, you
will benefit by reading the eBook Publisher 2.1 documentation/manual (User's Guide).
Ask away if you get stuck, either here or in a new thread.
Enjoy!